1. Field of the Invention
The present invention relates to an optical fiber array provided with a plurality of optical fibers that are aligned substantially in parallel with one another with a predetermined pitch therebetween, and more particularly, to an aligning implement for optical fibers that makes the fabrication of a optical fiber array easy, and to an optical fiber array fabricated by use of the aligning implement.
2. Description of the Related Art
As is well known, an optical fiber array is fabricated by use of an aligning implement or element that functions to align a plurality of optical fibers substantially in parallel with one another with a predetermined pitch therebetween. An optical fiber array is used, for example, in an optical module that is capable of transmitting and/or receiving a plurality of optical signals in order to transmit a plurality of optical signals emitted from a surface light emitting type optical element such as, for example, a laser diode array to an external circuit, device, apparatus or the like or to enter a plurality of optical signals transmitted from an external circuit, device, apparatus or the like into a surface light receiving type optical element such as, for example, a photodiode array. In addition, an optical fiber array is also used in an optical connector or in case of connecting two optical fiber arrays with each other.
FIG. 1 is a front view showing a prior art optical fiber array fabricated by use of a prior art aligning implement for optical fibers, and FIG. 2 is a front view showing the prior art optical fiber array in FIG. 1 in a state that a V-groove formed substrate and a lid member of the aligning implement for optical are being separated. The aligning implement 10 for optical fibers used in this optical fiber array comprises a V-groove formed substrate 12 having a plurality of (eight, in this example) V-grooves (each having a V-shape in section) 14 formed substantially in parallel with one another with a predetermined pitch therebetween on one surface (top surface in the figure) of a substrate (for example, a single crystal silicon substrate) having a generally rectangular or square shape in plan, for example, and a lid member 13 having a generally rectangular or square shape in plan, that is mounted on the top surface of the V-groove formed substrate 12.
A plurality of (eight, in this example) optical fibers 11 are disposed in the corresponding V-grooves 14 of the V-groove formed substrate 12, respectively, and the lid member 13 is mounted and fixed on the top surface of the V-groove formed substrate 12 in such manner that the lid member 13 covers the surface of the V-grooves 14. As a result, as shown in FIG. 1, each optical fiber 11 is located and secured in the corresponding V-groove 14, and the plurality of optical fibers 11 are aligned with a predetermined pitch therebetween and an optical fiber array is thus fabricated. Since the V-grooves 14 have been aligned and formed with high accuracy, the plurality of optical fibers 11 positioned and secured in the respective V-grooves 14 have been aligned with a predetermined pitch therebetween with high accuracy. Further, in general, in case of fixing the optical fibers 11 each having a sheathing or jacket on the external surface thereof on the V-groove formed substrate 12 by use of an adhesive, the lid member 13 is adhered and fixed on the V-groove formed substrate 12 together with the optical fibers 11 by the adhesive flowing toward the V-grooves 14 of the V-groove formed substrate 12 and the lid member 13. It is needless to say that the lid member 13 may be fixed on the V-groove formed substrate 12 by use of any other means.
Next, a manufacturing method of the above-described optical fiber array will be described in detail with reference to FIGS. 3 to 5. FIG. 3 is a plan view showing the V-groove formed substrate 12 shown in FIGS. 1 and 2, FIG. 4 is a plan view showing a state that the optical fibers 11 have been aligned on the V-groove formed substrate 12 shown in FIG. 3, and FIG. 5 is a plan view showing a state that the lid member 13 has been mounted on the V-groove formed substrate 12 in such manner that the lid member 13 covers the surface of the V-grooves 14 of the V-groove formed substrate 12. As shown in FIG. 3, the V-groove formed substrate 12 is a plate-like substrate having a generally square shape in plan in this example, and on about the central portion thereof is formed a step portion 15 extending linearly from the upper end thereof to the lower end thereof so that two areas the thickness (height) of which differs from each other are formed on both sides of the linear step portion 15. Each of the areas has a generally rectangular shape in plan. In the illustrated example, the two areas 12L and 12R each having a generally rectangular shape in plan are formed on the left-hand side and right-hand side of the step portion 15 respectively, and a plurality of (eight, in this example) V-grooves 14 are formed with a predetermined pitch therebetween with high precision on the left-hand side area 12L. The right-hand side area 12R of the V-groove formed substrate 12 has its thickness thinner (its height lower) than that of the left-hand side area 12L on which the V-grooves 14 are formed.
The reason that a difference in thickness or level is provided between the left side area 12L and the right side area 12R of the V-groove formed substrate 12 is such that as shown in FIGS. 1 and 2, the optical fibers 11 can be closely positioned and fixed in the corresponding V-grooves 14, that is, the optical fibers 11 can be positioned and fixed in the corresponding V-grooves 14 in such manner that each optical fiber is in contact with the both wall surfaces of the corresponding V-groove. As shown in FIGS. 4 and 5, since only the optical fibers (the core and the cladding covering the exterior surface thereof) 11 are disposed in the V-grooves 14, it is difficult to closely locate and secure the optical fibers 11 in the corresponding V-grooves 14 when the surface of the V-grooves 14 is covered with the lid member 13 unless the thickness of the right side area 12R of the V-groove formed substrate 12 on which the sheathings (jackets) 11B covering the optical fibers 11 and having larger diameters are put is thinner than that of the left side area 12L (unless the height of the right side area 12R is lower than that of the left side area 12L). Accordingly, it is preferred that the difference in thickness or height between the left side area 12L and the right side area 12R of the V-groove formed substrate 12 is set to be equal to or somewhat larger than a difference between the diameter of the optical fiber 11 and the diameter of the jacket 11B.
As shown in FIG. 4, the optical fibers 11 are disposed in the corresponding V-grooves 14 of the V-groove formed substrate 12 shown in FIG. 3 respectively as well as the jackets 11B of the optical fibers 11 are disposed on the right side area 12R, and then the optical fibers 11 are aligned. Next, as shown in FIG. 5, the lid member 13 is mounted on the left side area 12L of the V-groove formed substrate 12 in such manner that the lid member 13 covers the surface of the V-grooves 14 of the V-groove formed substrate 12, and then it is fixed thereon by use of, for example, an adhesive. Thereafter, the portions of the optical fibers 11 projecting from the end surface of the left side area 12L of the V-groove formed substrate 12 are severed and removed, and thus, an optical fiber array is completed.
Further, after the projecting portions of the optical fibers 11 have been severed, it is preferred to abrade and polish the end surfaces of the optical fibers 11. In such case, the end surface of the left side area 12L (the end surfaces of the V-grooves 14) of the V-groove formed substrate 12 and the end surface of the lid member 13 may be abraded and polished together with the end surfaces of the optical fibers 11.
In case of fabricating an optical fiber by use of the V-groove formed substrate 12 like the above prior art, it is required to dispose the optical fibers 11 in the corresponding V-grooves 14 of the V-groove formed substrate 12 one by one and to align the jackets 11B of the optical fibers 11 on the V-groove formed substrate 12 with accuracy. Since the width of each V-groove 14 is very narrow and the diameter of each optical fiber 11 is much smaller, the above-described work or job is very complicated and troublesome, and hence there are problems that it takes a lot of time as well as great skill is required.
On the other hand, another prior art aligning implement for optical fibers is described in, for example, Japanese Patent Application Publication No. 02-26395 (26395/1990). Unlike an aligning implement for aligning a plurality of optical fibers in a line as the above-described prior art, this another prior art aligning implement functions to align a plurality of optical fibers in plural lines. The prior art aligning implement disclosed in Japanese Patent Application Publication No. 02-26395 will be briefly explained with reference to FIGS. 6 to 8.
As shown in FIG. 6, in the prior art aligning implement for optical fibers, there is provided a positioning plate 20 in which a plurality of through holes 21 each having a generally rhombic shape in section are formed in a matrix manner (in this example, a matrix of 4×8) through a substrate 22 having a generally rectangular shape in plan, and the aligning implement for optical fibers is constructed by use of two positioning plates 20. As shown in FIG. 7, the two positioning plates 20A and 20B are laid one on top of the other in the state that the rhombic through holes 21A and 21B (see FIG. 8) of the two positioning plates 20A and 20B are aligned with each other, and then optical fibers 11 are inserted into corresponding through holes 21A and 21B one fiber for one hole. Thereafter, as shown in FIG. 8 by an arrow 23, the front side positioning plate 20A, for example, is moved in the direction of an extension of a diagonal line connecting between two opposed acute angles of each through hole 21B. As a result, each optical fiber 11 is caught and held between the wall surfaces of each through hole 21A of the front side positioning plate 20A, the wall surfaces forming one of the two acute angles of each through hole 21A, and the wall surfaces of each corresponding through hole 21B of the rear side positioning plate 20B, the wall surfaces forming the opposite angle of the two acute angles of each through hole 21B, as shown in FIG. 8. Thus, the 32 optical fibers 11 can be aligned in four rows each having eight optical fibers, namely, in a matrix of 4×8. It goes without saying that if there is used a positioning plate in which a plurality of through holes 21 each having a generally rhombic shape in section are formed in a line through a substrate 22 having a generally rectangular shape in plan, a plurality of optical fibers 11 can be aligned in a line.
In case a plurality of optical fibers are aligned in a line or plural lines by use of two positioning plates as described in the above Japanese Patent Application Publication No. 02-26395, the plurality of optical fibers are merely inserted into the corresponding through holes each having a generally rhombic shape of the two positioning plates that are laid one on top of the other. Therefore, it is unnecessary to align the optical fibers one by one on a V-groove formed substrate with high accuracy as in the first prior art described above. Consequently, there is no need for carrying out a work or job that is very complicated and troublesome and takes a lot of time, and also great skill is not required. Accordingly, it is possible to align a plurality of optical fibers comparatively with ease.
However, in the prior art disclosed in the above Japanese Patent Application Publication No. 02-26395, forces or pressures of opposite directions are applied to each optical fiber at different positions thereof in the axial direction from the side of the optical fiber by the two positioning plates, that is, a couple of forces is applied to each optical fiber. As a result, there occurs a problem that positioning of the optical fibers cannot be accomplished with high precision for reason that ends of optical fibers are deviated or deflected due to a bending moment of the couple, for example.